The present invention relates to a booster device for a hydraulic circuit, and a hydraulic circuit and a hydraulic hybrid automotive vehicle comprising such a booster device.
In general, hydraulic circuits comprise a system having a pump which draws fluid from a low pressure part of the circuit to generate pressure in a high pressure part of the circuit, the high pressure being stored in an high pressure accumulator in order to supply at least one receiver comprising a return line towards the low pressure part.
This type of hydraulic circuit, used in the industry or for different types of vehicles, in particular to provide traction to hydraulic hybrid automotive vehicles, can comprise a low pressure part maintained at a minimum pressure by a booster device in order to supply the pump at this minimum pressure to avoid cavitation of the fluid, in particular with the highest flows.
A known type of booster device comprises an accumulator pressurized by a gas, connected to the low pressure part of the circuit in order to maintain a minimum pressure in this part. However, the occupied space and mass of this accumulator are disadvantageous, in particular for an automotive vehicle. In addition, the pressure maintained by the gas is heavily dependent on the temperature and makes the functional parameters of the hydraulic circuit difficult to optimize.
Another known booster device, presented in particular in French Pat. No. FR2978506, comprises a booster pump drawing the fluid from a reservoir at atmospheric pressure, with the shaft aligned to the high pressure pump shaft and driven by an electric motor. This device requires an electric motor with its controls, which consumes electric energy and has a certain cost.